Battery supported power supplies are used for a variety of applications. Often a battery power supply must be regulated prior to being utilized in a system. For example, an exemplary system that utilizes voltage regulators in a battery supported power system 100 is shown in FIG. 1. As shown in FIG. 1, an AC power source may be obtained from an AC adaptor 110 which may be coupled, for example, to the public AC power grid. A battery 120 is also provided to provide a battery power source. As is known in the art, switches 112, 114, and 1116 and charger regulator 130 may be provided to select AC power from the AC adapter 110 or battery power from the battery 120 to provide the power for the supply rail Vin 125. As is also known, the switches may also be controlled to provide charging of the battery. For example, AC and battery supplied power systems are described in co-pending U.S. patent application Ser. No. 11/058,781, filed Feb. 16, 2005 entitled “Systems and Methods for Integration of Charger Regulation Within a Battery System” by Luo et al., the disclosure of which is expressly incorporated herein by reference.
As shown in FIG. 1, the power supply rail Vin 125 may be provided to a number of voltage regulators 140. In typical applications the rail Vin 125 may range from 9-20 volts. For example, when the AC adaptor 110 is being utilized the nominal input voltage level of Vin 125 may be 19.5V. However when the power supply system is supported by the battery, the minimum input voltage level may be as low as 9V. The voltage regulators 140 convert the voltage level of the rail Vin 125 to the necessary voltages required by battery supported power system 100 loads such as processor, chipsets, double data rate (DDR) memory and graphics cards. For example as shown in FIG. 1 the voltage regulators 140 are used to provide a number of regulated power supply rails ranging from 0.9-5V. The number, types, and output voltage levels of the regulators shown in FIG. 1 are merely exemplary and may vary depending upon a user's application and needs. One exemplary type of regulator in which the method introduced in this disclosure can be used is a general switching voltage regulator where Metal Oxide Silicon Field Effect Transistor (MOSFET) is used as power control switch. In one exemplary embodiment the voltage regulators may be “Buck” voltage regulators. Buck or “step-down” voltage regulators are regulators that are generally known to have an output voltage that is lower than an input voltage. Exemplary voltage regulators use controllers such as the Intersil ISL88550A, Maxim MAX8743 and the Texas Instrument TPS51116. The exemplary voltage regulators have a common feature that two auxiliary +5V power supply voltages are needed to support drive circuitry and control circuitry operations in the controller. Of these two power supply voltages, a +5V supply voltage called VCC or AVDD is the one after a RC filter. It will be recognized however that the concepts described herein are relevant to a wide range of other regulator types and that the regulators discussed herein are merely exemplary.
As shown in FIG. 1, the voltage regulators may receive power supply inputs in addition to the power circuitry input Vin rail that is being regulated. Thus, for example, as shown a Vdd supply input 142 may be utilized and a Vcc supply input 144 filtered by a RC filter after Vdd may also be utilized. As shown in more detail with regard to FIG. 2, the Vdd supply input 142 may act as a power supply for the MOSFET gate drive circuitry and the Vcc supply input 144 may act as a power supply for the analog and/or digital control circuitry within the regulator.
FIG. 2 shows an exemplary application for regulator 140. As shown in FIG. 2 the regulator 140 may include a regulator integrated circuit 210, power MOSFETs 220 and 222 and a regulator system output 230. Power supply rails Vin 125, Vdd 142, and Vcc 144 are provided to the regulator integrated circuit 210 as shown. The MOSFETs 220 and 222 are controlled be gate driver outputs 221 and 223 respectively. The source of MOSFET 220 and drain of MOSFET 222 are also coupled to the regulator integrated circuit 210 at the LX pin 225 as shown. The OUT pin 226 senses the output voltage to determine if the regulator operates normally, otherwise a protection action may be taken by the control circuitry inside the controller. The FB pin 228 provides feedback to the control unit through a voltage divider (not shown). The control unit will compare the feedback signal with a preset reference voltage to determine the on-time duration for the high side switching MOSFET 220 and the low side MOSFET. The exemplary voltage regulator 140 may use, for example, a MAXIM MAX8550 voltage regulator integrated circuit. As shown in FIG. 2, drive circuitry 240 may be provided to provide the gate driver output voltages. Control unit 250 may provide the control signals for controlling the drive unit 240 appropriately in response to the signals on the OUT 226 AND FB 228 pins. The Vdd supply 142 may be provided as a supply for the drive unit 240 and the Vcc supply 144 after a RC filter on Vdd may be provided as a supply for the control unit 250.
The power efficiency of the regulator 140 is dependent (among other things) upon the MOSFET conduction loss. In particular, the drain-source resistance Rds(on) of MOSFET 222 can greatly impact the over all efficiency of the overall power supply system and corresponding impact the battery life of the battery utilized in such systems. It would be desirable to provide techniques that improve the efficiency of power supply systems, in particular the voltage regulation efficiency.
As shown in FIG. 1, the battery supported power supply system may be utilized to generate a variety of system output voltages such as CPU voltage rails, system voltage rails, chipset voltage rails, memory voltage rails, graphics card voltage rails, etc. Such output voltages are often used in information handling systems. As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.